Terminal and method for managing cell information in terminal

ABSTRACT

The present invention relates to a method for managing cell informations received from neighbor cells for MDT (Minimization of Drive Test) in the 3GPP system and terminal for performing the method, the terminal including a transceiver which receives cell informations transmitted by at least one neighbor base station; a controller which checks at least one cell information for generating location prediction information to check current location of the terminal among the cell informations received by the transceiver; and a memory which stores the at least one cell information for generating the location prediction information as Minimization of Drive Test (MDT) measurement sample for reporting radio environment under the control of the controller. The terminal is capable of logging the neighbor cell measurement information efficiently depending on whether the terminal logs RF fingerprint information in the idle mode.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 13/824,596, filed on Mar. 18, 2013, which is a U.S. NationalStage application under 35 U.S.C. §371 of an International applicationfiled on Oct. 5, 2011 and assigned application number PCT/KR2011/007346,which claimed the benefit of a Korean patent application filed on Oct.8, 2010 in the Korean Intellectual Property Office and assigned Serialnumber 10-2010-0098490 and of a Korean patent application filed on Nov.4, 2010 in the Korean Intellectual Property Office and assigned Serialnumber 10-2010-0108965, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a terminal and cell informationmanagement method thereof. In more particular, the present inventionrelates to a terminal and method of managing cell information onneighbor cells for Minimization of Drive Test (MDT) measurement report.

2. Description of the Related Art

Typically, the mobile communication system has been developed for theuser to communicate on the move. With the rapid advance of technologies,the mobile communication system has evolved to the level capable ofproviding high speed data communication service as well as voicecommunication service. Recently, the 3GPP, as one of the next generationmobile communication standardization organizations, is in the progressof standardization of Long Term Evolution-Advanced (LTE-A). LTE-A is oneof the high speed packet-based communication technologies supportingdata rate higher than that of the current mobile communicationtechnology.

With the evolvement of the 3GPP standard, many discussions are beingconducted for optimizing the radio network in addition to the effort forincreasing data rate. In the initial radio network configuration oroptimization stage, a base station or a base station controller shouldcollect radio environment information related to its own cell coverage,and this process is called Drive Test. Since the conventional drive testis performed in such a way that an operator carries the test apparatuseson a vehicle while performing the measurement task repeatedly for longtime. The measurement result is used to configure the system parametersof the base stations or base station controllers. Such a conventionaldrive test increases total costs and time of the radio networkoptimization and maintenance.

Study on minimization of drive tests and enhancement of radioenvironment analysis process and manual configuration is being conductedin the name of MDT (Minimization of Drive Test). In more detail, theterminal measures the cell information and supplementary information onthe neighbor eNBs. The terminal reports the radio channel measurementinformation to the eNB periodically or immediately in response to aspecific event or after a predetermined time has elapsed from the timepoint when the radio channel measurement information has been logged. Atthis time, the UE operation of transmitting the measured cellinformation and other supplementary information to the UE is referred toas MDT measurement information report. If it is in the state capable ofcommunicating with the eNB, the terminal transmits the neighbor cellinformation measurement result to the eNB immediately. Otherwise, if itis not in the state capable of communicating with the eNB, the terminalretains the logged measurement information and, when it becomes possibleto communicate with the eNB, transmits the retained MDT measurementreport. The eNB uses the MDT measurement information received from theUE for cell coverage optimization.

However, the restrictive storage space of the terminal limits theneighbor cell information amount to be logged. This may cause an errorin cell area optimization of the eNB with the cell informationtransmitted by the terminal. There is therefore a need of a method forthe terminal to log the cell information for MDT efficiently.

The present invention proposes a terminal and method for the terminal tolog the neighbor cell measurement information efficiently.

In order to solve the above problems, a cell information managementterminal a transceiver which receives cell informations transmitted byat least one neighbor base station; a controller which checks at leastone cell information for generating location prediction information tocheck current location of the terminal among the cell informationsreceived by the transceiver; and a memory which stores the at least onecell information for generating the location prediction information asMinimization of Drive Test (MDT) measurement sample for reporting radioenvironment under the control of the controller.

In order to solve the above problems, a cell information managementmethod includes receiving cell informations of at least one neighborbase station; determining whether a location prediction information isdetermined with locations informations of the received cell informationsand the at least one cell information; and logging, when the locationprediction information is determined, the at least one cell informationdetermined for the location prediction information as a Minimization ofDrive Test (MDT) measurement sample for reporting radio environment.

According to the present invention, the UE is capable of storing thecell information for MDT measurement report efficiently. The UE is alsocapable of checking and storing the cell informations of eNBs aroundefficiently even when the current location is not acquired accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a signaling diagram illustrating the cell informationmeasurement method in a mobile communication system according to anembodiment of the present invention;

FIG. 2 is a diagram illustrating the mobile communication system forchecking the location of a UE according to an embodiment of the presentinvention;

FIG. 3 is a flowchart illustrating the measured cell information storagemethod of the UE according to the first embodiment of the presentinvention;

FIG. 4 is a flowchart illustrating the measured cell information storagemethod of the UE according to the second embodiment of the presentinvention;

FIG. 5 is a flowchart illustrating the measured cell information storagemethod of the UE according to the third embodiment of the presentinvention;

FIG. 6 is a block diagram illustrating the configuration of the UEaccording to an embodiment of the present invention;

FIG. 7 is a flowchart illustrating the measured cell information storagemethod of the UE according to the fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. Detailed descriptionof well-known functions and structures incorporated herein may beomitted to avoid obscuring the subject matter of the present invention.Furthermore, terms used herein are defined by taking functions of thepresent invention into account and can be changed according to thepractice or intention of users or operators. Therefore, definition ofthe terms should be made according to overall disclosures set forthherein.

The present invention relates to a method for managing the cellinformations on the neighbor eNBs in the MDT measurement report of the3GPP system. In more particular, the present invention proposes a methodfor logging the cell informations of neighbor eNBs efficiently dependingon whether the terminal in the idle mode logs RF fingerprintinformation.

In LTE-A, the basic MDT measurement sample report operation isclassified as shown in table 1 depending on the User Equipment RadioResource Control (UE RRC) state.

TABLE 1 MDT measurement information report RRC state of UE operation ofUE Idle mode Logging and deferred reporting Connected mode Immediatereporting

In table 1, the state where the UE does not communicate with the eNB isreferred to as idle mode, and the state where the UE can communicatewith the eNB is referred to as connected mode. In the case of MDT, theUE's measurement cell information is transmitted to the eNB throughRadio Resource Control (RRC) signaling. In the idle mode, however, theUE cannot transmit the corresponding cell information to the eNB.According, the UE logs the measured cell information and defersreporting the measured cell information until the operation statetransitions to the connected mode.

FIG. 1 is a signaling diagram illustrating the cell informationmeasurement method in a mobile communication system according to anembodiment of the present invention. In more detail, FIG. 1 is asignaling diagram illustrating the MDT measurement sampletransmission/reception method in a mobile communication system includinga UE and an eNB.

Referring to FIG. 1, the User Equipment (UE) 100 receives MDTmeasurement configuration information necessary for configuring MDT fromthe eNB at step 110. Here, the MDT measurement configuration informationincludes absolute timing, sampling cycle, measurement duration, etc. Theabsolute timing is used to acquire synchronization between the eNB 105and the UE 100. The sampling cycle is used for periodic downlink pilotsignal measurement, and the cell information for MDT is collected atpredetermined sampling cycle. The measurement duration is the timeduration for performing MDT. If the measurement duration expires, the UE100 stops MDT.

If the RRC state of the UE 100 transitions from the connected mode tothe idle mode, the UE 100 releases the connection with the eNB 105 andstarts MDT at step 115 at step 115. The UE 100 acquires the cellinformation on the neighbor eNB through the first MDT measurement sampleat step 220. Next, the UE 100 performs MDT measurement at the samplingcycle to acquire the second MDT measurement sample at step 125. Next,the UE 100 logs the MDT measurement sample at step 130.

The UE 100 recovers the connection with the eNB 105 at step 135. Next,the UE sends the eNB 105 the indication on whether there are availablelogs at step 140. At this time, the eNB 105 may request the UE 100 toperform MDT measurement report depending on the situation.

If the MDT measurement report request is received from the eNB 105, theUE reports the MDT measurement samples logged until then to the eNB 105.The UE 100 deletes the reported MDT measurement samples. In contrast, ifthere is no MDT measurement report request from the eNB 105, the UE 100retains the logged MDT measurement samples. In more detail, the UE 100releases the connection with the eNB 105 and starts MDT at step 145. Ifthe MDT measurement duration has not expired, the UE 100 performs MDTmeasurement for collecting the MDT measurement sample at step 150. Atthis time, the MDT measurement duration can be configured inconsideration of the connected mode execution time or not.

If the MDT measurement duration expires at step 155, the UE 100 stopsthe MDT measurement. Next, the UE 100 operates in the connected modewith the eNB 105 at step 160. At this time, the UE 100 notifies the eNB105 that there are logged MDT measurement samples at step 165. If theeNB 105 requests for MDT measurement samples, the UE 100 reports thelogged MDT measurement samples to the eNB 105.

The UE 100 in the idle mode logs the MDT measurement sample for themeasurement duration. The UE 100 performs downlink pilot signalmeasurement for the measurement duration in the connected mode or idlemode. the UE 100 also measures and collects the cell informationnecessary for the service area optimization for the measurement durationrepeatedly. The measurement duration value for performing the MDTmeasurement is referred to as MDT measurement duration and is acquiredfrom the channel measurement configuration information transmitted bythe eNB. The MDT measurement sample logged for service area optimizationincludes the cell informations as follows:

(1) Serving eNB Identifier; global cell ID information

(2) Measurement result

-   -   radio channel status information: Serving eNB signal strength        (i.e. RSRP; Reference Signal Received Power) and signal quality        (i.e. RSRQ; Reference Signal Received Quality) measurement        information    -   per-neighbor eNB radio channel status information:        Intra-freq/inter-freq/inter-RAT (Radio Access Technologies)        neighbor eNB identifier PCI (Physical cell ID), Carrier freq ID,        RAT type information, signal strength (i.e. RSRP) and signal        quality (i.e. RSRQ) measurement information

(3) Location info.

(4) Time Stamp

The MDT measurement sample basically includes the global cell ID of theserving eNB to indicate which eNB has sent the corresponding cellinformation. Here, the global cell ID is the unique eNB ID. The radiochannel status information is represented by a specific measurement. Forexample, the radio channel status of the service eNB can be representedby RSRP and RSRQ in E-UTRA, RSCP (Received Signal Code Power) and energyto noise ratio (Ec/No) in UTRAN, and Rxlev in GERAN. Although thedescription is directed to the E-UTRA LTE system herein, the presentinvention can be applied to other systems. The MDT function is expectedto be applied to the 3GPP LTE and UMTS (Universal MobileTelecommunications System).

The MDT measurement sample includes the Intra-freq/inter-freq/inter-RATneighbor eNBs' PCI (Physical cell ID), signal strength (i.e. RSRP), andsignal quality (i.e. RSRQ) measurement information. Particularly, theMDT measurement sample is capable of further includinginter-freq/inter-RAT neighbor eNBs' carrier frequency ID and RAT typeinformation. How many Intra-freq/inter-freq/inter-RAT neighbor eNBs'informations are included can be determined according to any offollowing methods.

(1) Designation of maximum number of neighbor eNBs to be included in MDTmeasurement sample

(2) Designation of neighbor eNBs as many as equal to or greater thanpredetermined threshold value

(3) Designation of neighbor eNBs as man as equal to or less than offsetwith serving eNB

(4) Combination of aforementioned methods

In the MDT measurement sample from the eNB, the location information isone of the important factors. If it fails to acquire the locationinformation based on the Global Positioning System (GPS), the UE 100measures and reports a set of signal strengths of the neighbor eNBs tothe serving eNB. Here, the set of signal strengths of the neighbor eNBsis referred to as RF fingerprint.

The eNB 105 which receives the RF fingerprint knows the locations of theneighbor eNBs already. The eNB 105 is capable of predicting thedistances between the UE and the neighbor eNBs by applying the signalstrength values of the neighbor eNBs to the signal pathloss model. TheeNB 105 is capable of acquiring coarse location of the UE through amethod such as triangulation based on the location informations of theneighbor eNBs and distances between the UE 100 and the neighbor eNBs.

FIG. 2 is a diagram illustrating the mobile communication system forchecking the location of a UE according to an embodiment of the presentinvention. In more detail, FIG. 2 is a diagram illustrating theprocedure of collecting RF fingerprint for predicting the location ofthe UE and reporting the RF fingerprint.

If it is impossible to acquire its location based on the GPS, the UE iscapable of transmitting the RF fingerprint, instead of accurate locationinformation, to the serving eNB. The serving eNB is capable ofpredicting the location of the UE using the received RF fingerprint. Theterms “RF fingerprint” and “location prediction information” can be usedinterchangeably in the same meaning.

Referring to FIG. 2, the UE 205 in the idle mode which is performing MDTmeasurement collects and logs the RF fingerprint from the neighbor eNBs215, 220, and 225. Afterward, the UE 205 enters the connected mod torecover the connection with the serving eNB 210. In the connected mode,the UE 255 transmits the logged RF fingerprint to the serving eNB 260.Although the description is directed to the case where the UE 250 in theidle mode collects the RF fingerprint, the terminal 255 in the connectedmode is also capable of collecting and transmitting the RF fingerprintto the serving eNB 210 and 260.

In FIG. 2, it is assumed that the UE 250 in the idle mode has camped onthe cell of the first serving eNB 210. The UE 205 in the idle modereceives the E-UTRAN Cell Global Identifier as the cell information inthe MDT measurement sample transmitted by the first serving eNB 210.Here, ECGI information is the unique identifier of the first serving eNB210. The UE 205 in the idle mode collects the signal strength value,i.e. RSRP, of the first serving eNB 210.

The UE 205 in the idle mode collects the cell information, i.e. PhysicalCell Identity (PCI) information and RSRP values, in the MDT measurementsample from the neighbor eNBs 215, 220, and 225 at steps 235, 240, and245. The PCI is the eNB identifier such as ECGI.

The ECGI is a unique value assigned per eNB while the PCI can bereusable such that plural eNBs may use the same PCI value. The ECGI isused to identify each eNB and has a relatively long value. Accordingly,it is burdensome to use ECGI at every session establishment in view ofresource efficiency. As a consequence, ECGI is used in the initialconfiguration for communication and, afterward, PCI which is relativelyshort is used for discriminating among the eNBs. The PCI is too short todiscriminate among all eNBs so as to be reused. Accordingly, in order toavoid confusion, the same PCI is allocated to the eNBs far enough fromeach other.

The UE 205 in the idle mode checks the location within the service areausing the ECGI information of the first serving eNB 210. The UE 205 inthe idle mode collects the PCI values of the neighbor eNBs to check theneighbor eNBs around the UE 205.

The RF fingerprints collected at step 230, 235, 240, and 245 can betransmitted to the second serving eNB 260 when the UE 205 in the idlemode enters the connected mode. Here, the first and second serving eNBs210 and 260 are identical with or different from each other. If thefirst and second serving eNBs 210 and 260 are different from each other,this means that the UE has performed handover from the first eNB 210 tothe second serving eNB 260.

The UE 255 in the connected mode is capable of transmitting the locationprediction information, i.e. RF fingerprint, along with the logged MDTmeasurement sample at step 265 according to the request from the secondserving eNB 260. For reference, the current LTE standard restricts thenumber of eNBs that can be included in the RF fingerprint to 6.

If plural intra-freq neighbor eNBs are selected regardless of thecriteria, the cell informations of the selected intra-freq neighbor eNBsare included in the MDT measurement sample. In the case that the UEcannot acquire Global Navigation Satellites System (GNSS) locationinformation, the UE includes the RF fingerprint consists of the PCIs andRSRP values of 6 intra-freq neighbor eNBs instead of accurate locationinformation, in the MDT measurement sample. According to an embodimentof the present invention, the RF fingerprint is included in the MDTmeasurement sample, the UE is capable of reusing the cell information ofthe intra-freq neighbor eNBs. In this case, it is possible to reduce thesize of the MDT measurement sample to be stored in the UE.

That is, the MDT measurement sample 130 described with FIG. 1 includes alocation Information Element (IE) containing the location informationand a field containing the cell information of neighbor eNBs. The RFfingerprint can be logged in the location information IE or at a part ofthe neighbor cell measurement information field. Regardless of the fieldcontaining the RF fingerprint, there is no need to log the neighbor cellinformation and included in the RF finger print in the neighbor cellmeasurement information field of specific MDT same sample redundantly.Accordingly, if it is necessary for logging the RF fingerprint insteadof the GNSS location information, the UE includes, among the neighborcell informations collected at Discontinuous Reception (DRX) period, the6 intra-freq neighbor cell informations in the RF finger print. The UEalso includes only the neighbor cell measurement information as the MDTmeasurement sample in the neighbor cell measurement information fieldadditionally.

The intra-freq neighbor cells selected by one of the above-describedmethods and the 6 intra-freq neighbor cells determined by the RFfingerprint are determined according to different methods. The UE logsthe cell informations of the 6 intra-freq neighbor eNBs determined bythe RF fingerprint first in logging the cell informations of theneighbor eNBs as the MDT measurement sample. The UE is capable of savingthe memory for the MDT measurement sample by logging the cellinformation necessary among the non-logged cell informationsadditionally.

FIG. 3 is a flowchart illustrating the measured cell information storagemethod of the UE according to the first embodiment of the presentinvention. In more detail, FIG. 3 is a flowchart illustrating the methodfor logging the cell information efficiently when plural cells for MDTmeasurement sample exist. Here, Rule 1 is of the first cell informationmeasurement method operating in such a way of acquiring accuratelocation information based on GPS and measuring the cell informationfrom the neighbor eNBs, and Rule is of the second cell informationmeasurement method operating in such a way of acquiring the RFfingerprint as the location prediction information based on the cellinformation of the neighbor eNBs.

Referring to FIG. 3, the UE triggers the cell information to be loggedas MDT measurement sample according to Rule 1 at step 305. The UEdetermines whether the high priority cell information is triggeredaccording to Rule 2 at step 310. If the high priority cell informationis not triggered, the UE selects and stores the cell informations to belogged as MDT measurement sample according to Rule 1. However, if thecell information is triggered by Rule 2, the UE stores the cellinformations in the highest priority first order.

If the cell informations indicated by both the Rule 1 and Rule 2 arenecessary, the UE has to log the all necessary cell informations whilereducing the memory size. Accordingly, the UE checks whether the cellinformations according to Rule 1 includes the higher priority cellinformations according to Rule 2. If the cell informations according toRule 1 include the cell informations according to Rule 2, the UE logsall cell informations determined by Rule 1 that have low priority atstep 320.

In contrast, if the cell information according to Rule 1 includes notall the cell informations according to Rule 2, the UE stores all cellinformations with high priority according to Rule 2 as MDT measurementsample at step 325. The UE also includes the rest cell informations,with the exception of the cell information logged by Rule 2 among thecell information according to Rule 1, in the MDT measurement sampleadditionally. As described above, if the cell information acquiredthrough different methods are logged as described with reference to FIG.3, it is possible to avoid unnecessary redundancy of cell information.

A description is made of the method for the UE to store the RFfingerprint as MDT measurement sample hereinafter with reference to FIG.4.

The RF fingerprint as the location prediction information can be storedin the information containing the intra-freq neighbor cell measurementin the MDT measurement sample. If it is impossible to log the GNSSinformation, the UE changes the neighbor cell selection method toincluding the RF fingerprint in the intra-freq neighboring cellmeasurement.

For example, although the number of intra-freq neighbor eNBs to belogged in the intra-freq neighbor cell measurement is 3, the UE iscapable of extend the number of cells to 6 as many as necessary for theRF fingerprint. Also, the UE is capable of logging the signal qualityinformation of the three neighbor cell′ informations among the sixneighbor cell informations as many as necessary for the RF fingerprintto save memory. If the number of cell informations of the intra-freqneighbor cells to be logged according to the conventional neighbor cellselection method is equal to or greater than the number of neighbor cellinformations used as the RF fingerprint, the UE is capable of performingfull logging for the cell informations of the neighbor eNBs that are notincluded in the RF fingerprint.

FIG. 4 is a flowchart illustrating the measured cell information storagemethod of the UE according to the second embodiment of the presentinvention.

Referring to FIG. 4, the UE determines the number of intra-frequencyneighbor eNBs (n) to be measured for MDT measurement sample based on aspecific cell information measurement method (specific rule) at step405. Next, the UE determines whether the RF fingerprint with X cellinformations is determined as location information at step 410.

If the RF fingerprint with X cell informations is not determined, the UElogs the cell informations of n selected intra-freq neighbor eNBs (suchas PCI, signal strength information (i.e. RSRP), and signal quality(i.e. RSRQ)) as the MDT measurement sample. Otherwise, if the RFfingerprint with X cell informations is determined, the UE determineswhether the number of measured intra-freq eNBs' cell informations isgreater than X at step 415.

If the number of measured intra-freq eNBs' cell informations is greaterthan X, the UE logs the measured intra-freq neighbor eNBs' cellinformations (such as PCI, RSRP, and RSRQ) as the MDT measurement sampleat step 420.

Otherwise, if the number of measured intra-freq eNBs' cell informationsis not greater than X, the UE logs the X cell informations including PCIand signal strength information) that are determined for use in RFfingerprint as the MDT measurement sample at step 425. The UE is capableof logging the other cells' information without overlapping with the Xcell informations determined as RF fingerprint among the cellinformation of the measured intra-freq neighbor eNBs at step 430. Inthis way, it is possible to log the cell informations determined for theRF fingerprint and the intra-frequency neighbor eNBs' cell informationswithout overlapping.

A description is made of the case of logging the cell informations inthe information field and neighbor cell measurement field distinctlywith hereinafter with reference to FIG. 5. In more detail, the MDTmeasurement sample includes a location information filed for storing thelocation informations acquired from the RF fingerprint and a MDTmeasurement sample field for storing the neighbor cell measurement. Inthis case, the conventional cell selection method is used, however, theUE logs only the cell informations not included in the RF fingerprint asthe intra-freq neighbor cell measurement.

In the case that the RF fingerprint is included as location information,the intra-freq neighbor cell measurement includes only the signalquality. If the number of intra-freq neighbor eNBs' cell informations tobe logged is equal to or greater than the number of cell informations tobe included in the RF fingerprint, the UE performs the full logging onthe cell informations of the eNBs that are not included in the RFfingerprint.

FIG. 5 is a flowchart illustrating the measured cell information storagemethod of the UE according to the third embodiment of the presentinvention.

Referring to FIG. 5, the eNB sets the number of intra-freq neighbor eNBs(n) necessary for acquiring MDT measurement sample based on a specificcell information measurement method at step 505. Next, the UE determineswhether the RF fingerprint is determined with the X neighbor eNBs' cellinformations as location information at step 510. If the RF fingerprintis not determined with X neighbor eNBs' cell informations, the UE logsPCI, signal strength information (e.g. RSRP), and signal quality (e.g.RSRQ) of the selected intra-freq neighbor eNBs in the MDT measurementsample field at step 520.

If the RF fingerprint is determined with X neighbor eNBs' cellinformations, the UE determines whether the number of selectedintra-freq neighbor eNBs' cell informations is greater than the numberof cells to be included in the RF fingerprint X at step 515. If so, theUE logs the cell informations, i.e. PCI and signal strength information,of the X eNBs included in the RF fingerprint into the locationinformation field.

Next, the UE stores the signal quality information as the X eNBs' cellinformations included in the RF fingerprint in the MDT measurementsample field at step 530. The UE logs the PCI, signal strength (e.g.RSRP), and signal quality (e.g. RSRQ) as the rest intra-freq neighboreNBs' cell informations among the cell information logged not yet intothe MDT measurement sample field.

Otherwise, if the number of selected intra-freq neighbor eNBs' cellinformations is greater than the number of cells to be included in theRF fingerprint X, the UE logs PCI and signal strength information as theX neighbor eNBs' cell informations necessary for the RF fingerprint intothe location information field. Next, the UE logs the intra-freqneighbor eNBs' cell informations among the information logged not yetinto the MDT measurement sample field additionally at step 545. In thisway, it is possible to log the RF fingerprint and the intra-freqneighbor eNBs' cell informations without overlapping.

FIG. 6 is a block diagram illustrating the configuration of the UEaccording to an embodiment of the present invention.

Referring to FIG. 6, the transceiver (transmitter/receiver) 605 receivesthe cell informations transmitted by the neighbor eNBs. The transceiver605 is also capable of receiving the information on the current locationof the UE from the GPS.

The memory 610 stores the cell informations selected among the cellinformations measured by the transceiver 605 according to theinstruction from the controller 615. Here the selected cell informationsare the informations necessary for generating the MDT measurement sampleand include Global IDs for identifying the cells, PID, signal strength(e.g. RSRP), signal quality (e.g. RSRQ), UE location information, etc.

The controller 615 controls to store the neighbor eNBs' cell informationin the memory 610 efficiently according to the procedure proposed in thepresent invention. In more detail, if it fails the check the currentlocation of the terminal based on the GPS information, the control unit615 checks the neighbor eNBs' cell information to acquire the RFfingerprint as the location prediction information for determining theUE location. At this time, the number of cells required for the MDTmeasurement sample is predetermined. Accordingly, when storing the cellinformations as the MDT measurement sample in the memory 610, thecontrol unit 615 stores the cell informations included in the RFfingerprint in an order of priority. The control unit stores the othercell informations with the exception of the cell informations includedin the RF fingerprint among the measured neighbor eNBs' cellinformations in the memory 610.

When the above-structured UE stores the MDT measurement sample, themeasured cell informations and the cell informations included in the RFfingerprint can be stored without overlapping. Accordingly, it ispossible to adjust the space occupied by the MDT measurement sample.That is, the UE receives at least one neighbor eNB's cell information,determines whether the location prediction information is determinedwith the location information of the received cell information alongwith the at least one cell information, and logs, if the locationprediction information is determined, the at least one cell informationdetermined as the location prediction information as the MDT measurementsample for reporting the radio environment.

FIG. 7 is a flowchart illustrating the measured cell information storagemethod of the UE according to the fourth embodiment of the presentinvention.

Typically, the number of neighbor cells necessary for MDT is less thanthe number of neighbor cells necessary for the RF fingerprint. In thecase of the RF finger print, as the number of cells providing theinformation increases, the calculated location becomes more accurate.Accordingly, the more the number of cell informations, the better theresult is in measuring the cell information with the RF fingerprint.

However, in order to perform the MDT for service area optimization, itis enough to consider a few cells providing best signal strengths.Accordingly, the sell information measurement and storage method of theUE can be performed as shown in FIG. 7,

Referring to FIG. 7, the UE determines the number of intra-freq neighboreNBs (n) to be measured for MDT measurement sample based on a specificcell information measurement method (specific rule) at step 705. The UEreceives cell informations from the n neighbor eNBs for generating theMDT measurement sample.

Next, the UE determines whether the RF fingerprint is determined withthe X cell informations as location informations at step 710. At thistime, the number of neighbor eNBs' cell informations X to be used as theRF fingerprint is equal to or greater than the number of intra-freqneighbor eNBs measured for the MDT measurement sample.

If it is not necessary to use the RF fingerprint since the accurate UElocation is acquired based on the information from satellites, the UElogs the cell informations of the n selected intra-freq neighbor eNBs,i.e. PCI, signal strength (e.g. RSRP), and signal quality (e.g. RSRQ) asthe MDT measurement sample at step 715.

If the RF fingerprint is determined with the X neighbor cellinformations as location informations, the UE logs the X cellinformations determined for the RF fingerprint, such as the PCI andsignal strength information, as the MDT measurement sample at step 720.Next, the UE logs the other cell informations not overlapping with the Xcell informations for RF fingerprint among the measured intra-freqneighbor eNBs' cell informations additionally at step 725. In this way,it is possible to log the cell informations selected for the RFfingerprint and the intra-freq neighbor eNBs' cell information withoutoverlapping.

Although the description has been made with reference to particularembodiments, the present invention can be implemented with variousmodification without departing from the scope of the present invention.Thus, the present invention is not limited to the particular embodimentsdisclosed but will include the following claims and their equivalents.

What is claimed is:
 1. A terminal for managing cell information in acommunication system, the terminal comprising: a transceiver configuredto transmit and to receive a signal; and a controller configured to:control to receive cell information of at least one neighbor basestation, determine that location prediction information with the cellinformation of the at least one neighbor base station for generating thelocation prediction information is decided as location information, andlog, if the location prediction information is decided as the locationinformation, the cell information as a minimization of drive test (MDT)for a reporting radio environment.
 2. The terminal of claim 1, whereinthe controller is further configured to determine a number of the atleast one neighbor base station to be measured for the MDT.
 3. Theterminal of claim 1, wherein the cell information includes informationon at least one of physical cell identity (PCI), signal strength, orsignal quality.
 4. The terminal of claim 2, wherein the controller isfurther configured to: determine, if the location prediction informationis decided as the location information, that the number of the at leastone neighbor base station to be measured for the MDT is greater than anumber of the at least one base station for generating the locationprediction information; and log, if the number of the at least oneneighbor base station to be measured for the MDT is greater than thenumber of the at least one base station for generating the locationprediction information, the cell information of the at least oneneighbor base station for generating the location prediction informationand other cell information with the exception of the cell information ofthe at least one neighbor base station for generating the locationpredication information.
 5. The terminal of claim 4, wherein thecontroller is further configured to log, if the number of the at leastone neighbor base station to be measured for the MDT is equal to or lessthan the number of the at least one base station for generating thelocation prediction information, the cell information of the at leastone neighbor base station for generating the location predictioninformation.
 6. The terminal of claim 2, wherein the controller isfurther configured to log, if the location prediction information is notdecided as the location information, the cell information of the atleast one neighbor base station based on the number of the at least oneneighbor base station to be measured for the MDT.
 7. The terminal ofclaim 1, wherein the cell information comprises at least one of a basestation identifier for identifying the base station and a radio channelstatus information per base station.
 8. The terminal of claim 1, whereinthe receiving of the cell information comprises receiving, if theterminal is in an idle mode, the cell information periodically.
 9. Amethod of a terminal for managing cell information in a communicationsystem, the method comprising: receiving cell information of at leastone neighbor base station; determining whether location predictioninformation with the cell information of the at least one neighbor basestation for generating the location prediction information is decided aslocation information; and logging, if the location predictioninformation is decided as the location information, cell information asa minimization of drive test (MDT) for a reporting radio environment.10. The method of claim 9, further comprising: determining a number ofthe at least one neighbor base station to be measured for the MDT. 11.The method of claim 9, wherein the cell information includes informationon at least one of physical cell identity (PCI), signal strength, orsignal quality.
 12. The method of claim 10, wherein the logging of thecell information comprises: determining, if the location predictioninformation is decided as the location information, that the number ofthe at least one neighbor base station to be measured for the MDT isgreater than a number of the at least one base station for generatingthe location prediction information; and logging, if the number of theat least one neighbor base station to be measured for the MDT is greaterthan the number of the at least one base station for generating thelocation prediction information, the cell information of the at leastone neighbor base station for generating the location predictioninformation and other cell information with the exception of the cellinformation of the at least one neighbor base station for generating thelocation predication information.
 13. The method of claim 12, whereinthe logging of the cell information comprises: logging, if the number ofthe at least one neighbor base station to be measured for the MDT isequal or less than the number of the at least one base station forgenerating the location prediction information, the cell information ofthe at least one neighbor base station for generating the locationprediction information.
 14. The method of claim 10, further comprising:logging, if the location prediction information is not decided as thelocation information, the cell information of the at least one neighborbase station based on the number of the at least one neighbor basestation to be measured for the MDT.
 15. The method of claim 8, whereinthe cell information comprises at least one of a base station identifierfor identifying the base station and a radio channel status informationper base station.
 16. The method of claim 8, wherein receiving cellinformation comprises receiving, if the terminal is in an idle mode, thecell information periodically.